DESCRIPTION: (adapted from investigators application) Normal aerobic metabolism produces reactive oxygen species including superoxide anions, hydrogen peroxide and hydroxyl radicals. Besides normal metabolism, other sources of oxygen radicals include: ionizing radiation, Near UV, respiratory burst oxidase in phagocytes and neutophiles, drugs (i.e. antimalarial hydrazines and chemotheraputic agents) and dietary agents. Active species of oxygen will react with many biomolecules, including DNA, RNA, lipids and protein. These reactions cause mutations, tumors, lipid peroxidation and cell death. Active oxygen species are now widely believed to play a significant role in 'spontaneous' tumorogenesis. Aerobic organisms have evolved complex defense and repair systems to minimize oxidative damage. It is important to learn more about the cell's responses to oxidative stress, as it is such a ubiquitous stress. Dr. Farr has discovered a novel multigene response to an increase in the flux of superoxide radicals. He calls this response the 'SoxR' response (for superoxide response). The regulation of SoxR is distinct from previously identified stress responses, including that induced by hydrogen peroxide and other peroxidizing agents. The SoxR regulon includes several protective enzymes, genes regulating macromolecular synthesis and a novel DNA repair pathway. He has isolated and cloned three Mud(lacZ, Ap) fusions that respond specifically to superoxide radicals. These genes are distinct from others known to respond to superoxide including sodA (superoxide dismutase), nfo (endonuclease IV) and glucose- 6-phosphate dehydrogenase and NADPH-dependent diaphorase activities. Preliminary evidence presented in this proposal suggests that all the above genes share a common regulatory pathway and may form a regulon (the SoxR regulon). The overall aim of this research proposal is to investigate the genetic and biochemical nature of the regulation of this novel stress response as follows: I) to characterize regulatory mutants created by MNNG and Tnkan-induced mutagenesis in which expression of several soi (superoxide inducible) genes is altered. II) to characterize and sequence the soi promoter regions to determine if there is homology between them, and to map the actual regulatory region. III) to clone the regulatory element and to achieve overexpression of its gene product. IV) to purify the regulatory element(s) in order to study the mechanism(s) by which it regulates superoxide inducible genes, and to study the mechanism by which the regulatory element itself responds to an increase in the flux of superoxide radicals. V) to determine the relationship between the macromolecular synthesis operon and recovery of macromolecular synthesis after oxidative stress.